1.) How many terms of the sequence 18, 16, 14... must be taken so that their sum is 636?
2.) How many terms are there in the A.P. whose first and fifth terms are -14 and 2 respectively and the sum of the terms is 40?
3.) How many terms of the A.P. 9, 17, 25... must be taken so that their sum is 636?
4.) How many terms of the A.P. 63, 60, 57... must be taken so that their sum is 693?
5.) How many terms of the A.P. 27, 24, 21... should be taken so that their sum is zero?